1. Field of Endeavor
The present invention relates to a method for production of a supporting basket with round connectors for an end winding of a stator winding of an electrical machine, and also relates to a supporting basket having round connectors for an end winding of a stator winding of an electrical machine.
2. Brief Description of the Related Art
Large electrical machines such as generators and electric motors which are used in power stations have a stator with an electrical stator winding. This stator winding is passed out of the stator, at least at one axial end of the stator, where it forms an end winding. An end winding such as this is formed in particular by end sections of conductors, which are in the form of bars, of the stator winding, which are angled in the radial direction and in the circumferential direction such that the end winding is in the form of a truncated cone, which widens as the distance from the associated end-face stator end increases. A supporting basket is normally provided in order to support the end winding. This supporting basket may have a plurality of supporting brackets which are distributed in the circumferential direction and are arranged radially externally on the end winding. An axial support for the end winding can be provided, for example, via these supporting brackets at the associated front-side end of the stator. A supporting basket such as this normally has one or two supporting rings, which extend in the circumferential direction and to which the supporting brackets are attached. In this case, the supporting rings can support the supporting brackets radially, and thus allow them to absorb radial supporting forces.
In order to allow the stator winding to be electrically connected to an electrical system, for receiving the current produced by a generator and/or for providing the current required by an electric motor, the winding bar sections of the end winding are electrically connected at their bar ends, in a complex, predetermined manner, to a plurality of so-called round connectors, which themselves form electrical connections to the end winding. The stator winding can be connected to the electrical system via these connections, which are formed with the aid of the round connectors. The round connectors which are used in this case must be electrically insulated and must also be impregnated, in order to prevent the ingress of moisture.
In principle, it is possible to insulate the round connectors wet or dry as individual parts, for the production of the end winding. Wet-insulated round connectors are likewise dried and cured as individual parts. Wet insulated ground connectors in principle do not require any impregnation. In contrast to this, dry-insulated round connectors must additionally be impregnated. To do this, it is in principle possible to impregnate the dry-insulated round connectors individually and then to dry and cure them. An appropriate impregnation tool can be used for this purpose. In the case of long round connectors, it may be necessary to mechanically separate them before dry insulation, then to impregnate them and only then to join them together again, for example by welded joints or soldered joints. The weld or solder points must then be locally wet-insulated and dried, and cured.
For fitting of the end winding, it is also necessary to fit the supporting basket to the respective stator end, that is to say, to fit the supporting brackets and the supporting rings to the stator end. The completely insulated, and possibly impregnated, round connectors can then be fitted to the supporting basket, using appropriate attachment devices for this purpose. When the round connectors are being fitted, they can be moved along the supporting brackets. In order to prevent damage to the insulation and impregnation during this process, wet cushions can be used here. After the round connectors have been fitted, the attachment devices that are used are also locally wet-impregnated. The associated drying and curing of these local impregnation points can be carried out, for example, in the course of a heat treatment of the stator. Overall, a production process such as this is comparatively complex.